Am I overreacting or is this a genuine issue
My car does 0.4 km more per litre when my father in law is not in it.
I have twenty two data points. Tank to tank, same route, same fuel pump, same driver.
With him: 13.6 average. Without: 14.0. Every single time. Not once has it gone the other way.
He weighs 74 kg. I have accounted for this. My friend Suresh is 81 and the number does not move for Suresh.
I have tested the seat he sits in with other people. Fine. I have tested him in the rear. Same result. It is not the seat. It is him.
He does nothing wrong. He doesn't touch the AC. He barely talks. He looks out of the window and occasionally says "achha road hai."
Twice now I have said no to a family trip and given a reason that as not the reason.
Is there a mechanical explanation for this or should I stop logging it?